As a conventionally known structure for determining the authenticity of information storage cards such as magnetic cards, securities, tickets and commercial goods, Japanese Utility Model Laid Open Publication (Kokai) No. 61-182580 discloses an identification structure comprising a hologram which is adhered to an article as an identification seal, which is difficult to duplicate for an unauthorized person, and can be visually identified.
Japanese Patent Laid Open Publication (Kokai) No. 3-71383 by the Applicant of this application also discloses an identification structure comprising a hologram as an identification seal having a specific light diffractive property provided on the surface of an article, and optical identification means for determining the authenticity of the article by projecting a light beam upon the hologram and receiving the diffracted light therefrom.
In particular, according to the structure mentioned above, the unauthorized duplication of the identification seal is extremely difficult, and the identification of the authenticity of the article may be satisfactorily carried out up to a certain point since the same specific light diffractive property as well as the same visual appearance as the authentic identification seal must be duplicated for forging the identification seal.
According to this structure, however, the counterfeit of the identification means is not entirely impossible because the use of a specific light diffractive property of the hologram as the identification means can be easily recognized and the identification seal cannot be made entirely unavailable to the counterfeiter. Therefore, a more effective identification structure has been strongly desired.
Based on such considerations, the Inventors have found that unauthorized fabrication could be discouraged even more effectively when the authenticity of the light reflecting region or the article itself is determined by taking into account the plane of polarization of the diffracted light in addition to the specific light reflective directivity (or specific light diffractive property).